The effect of contrast material on transitional cell carcinoma viability.	In this study, increasing contrast concentration and/or exposure time decreased the growth and adherence of transitional cell carcinoma cells. Similarly, several authors have shown that the toxicity of contrast material to vascular endothelial cells in culture is related to concentration and time of exposure; this toxicity is minimized if non-ionic, low osmolar contrast is utilized. Identical trends of increasing toxicity with increasing osmolality have been documented with kidney cell lines, vascular smooth muscle cells, myocardial cells, neural cells, human fibroblasts, rat mesenchymal cells, and rat hepatocytes. The toxicity of contrast material in malignant cells (human cervical carcinoma cell lines and prostate cancer cell lines) has also been documented. Factors other than direct cellular toxicity may also affect the ability of malignant transitional cells transported with contrast material to implant on other sites in the collecting system. Zhan et al have evaluated neutrophil adhesion to contrast-exposed vascular endothelial cells. These authors observed increasing cellular adhesion with decreasing contrast dose. This was not related to osmolality as there was no similar endothelial adhesion activation with equal osmolality solutions of non-contrast solutions. The authors felt that contrast material, therefore, caused some form of modulation of cell adhesion molecules. This theory is supported by research by Owens et al that shows increases in the adhesive properties of endothelial cells to platelets after contrast exposure, and Rasmussen et al who found decreased granulocyte adherence with contrast exposure. In our study, transitional cell carcinoma cultures were placed on a collagen substrate to encourage adherence. There was an increasing number of non-adherent cells with increasing contrast concentration and exposure time, which suggests an effect of the contrast on cellular adhesion as well (Table 1). Potier et al found that rat mesangial cells were more sensitive to the cytotoxic effects of contrast agents than the less differentiated human fibroblasts were. This might suggest that the more poorly-differentiated transitional cell carcinoma cells would not be as sensitive to contrast material as low-grade tumors. However, we did not observe any differences in the responses of high- versus low-grade transitional cell tumors to exposure to contrast material. Intravenous contrast administration can lead to multiple adverse reactions, such as cardiotoxicy, nephrotoxicy, and hemodynamic toxicity. This makes non-ionic, low-osmolality agents preferable to ionic, high-osmolality agents. However, direct introduction of material into the urinary collecting system for the evaluation of transitional cell carcinoma may be less prone to seeding of viable malignant cells if ionic, high-osmolar contrast agents are utilized. Additional considerations include potential masking of very small filling defects in the upper urinary tract through opacification with extremely concentrated contrast material. Also, cytologic abnormalities are worsened by exposure to ionic, high-osmolar contrast agents, thus, any specimens for cytologic analysis should be collected prior to utilization of any contrast agents.	bladder